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Accuracy of OS Net, OSTN15 and OSGM15

Find out about the accuracy of our OS Net stations and coordinate transformations.

OS Net station coordinate accuracy

The standard errors for OS Net base station coordinates are generally better than 0.008m in plan and 0.020m in height.

Download OS Net RINEX data.

OSTN15/OSGM15 transformation accuracy

OSTN15 now defines OSGB36 National Grid – in conjunction with the OS Net stations.

You can consider OSTN15 to be somewhat error free. That is, when any GNSS positional errors are not included.

Agreement between OSTN15 and the old triangulation network stations is 0.1m rms (down to the third order) for Great Britain only.

The standard error in height of OSGM15 for each regional vertical datum are included in the table below. These errors are for OSGM15 only and do not include any GNSS heighting errors.

Regional height datum Standard error (m)

Great Britain






Outer Hebrides (Stornoway 15 datum)


Isle of Man